Machining dies and moulds can be expensive. The workpiece material is often costly, and programming and machining is complex. However, in a global marketplace, being able to offer toolmaking services at extremely competitive prices is paramount to business survival.
The most significant cycle time reductions when producing dies and moulds are made in roughing and semi-finishing, operations that remove the most material. However, the hardened steels used typically in toolmaking (>45 HRc) are inherently difficult to machine – moulds and dies are usually milled in their hardened state to prevent heat treatment from affecting geometry. As a consequence, the onus in recent years has been on cutting-tool manufacturers to deliver technologies able to accelerate this part of the process in materials such as P20, H13 and S7.
The right machining strategy is related directly to correctly chosen cutting tools. As a result, the cutter is a substantial factor of productivity and profitability. A high-feed and light cutting action is acknowledged as a successful formula in milling cutters used for such purposes. Here, the secret lies in a combination of optimized edge design and grade.
With this in mind, Sandvik Coromant said its cutter has 20% more productivity than comparable competitor tools. The product offers a cost-effective way to increase the speed of machines.
Coro Mill 419 is a high feed indexable cutter with five edges per insert for added economy. It is designed specifically for exceptional performance when roughing and semi-finishing hardened steels, according to the supplier. The cutter’s long life inserts are both strong and robust for reliable machining at depths of cut up to 2mm. Recommended feed rates (fz, feed per tooth) in face milling applications are quoted in the region of 0.5 – 1.1mm/z using parallel land inserts. Radius inserts are recommended in profile milling applications.
The cutter’s ability to minimize axial forces comes from deploying a 19° lead angle and a positive axial inclination angle, the company said, explaining that low lead angles generate a much thinner chip, which in turn necessitates higher feed rates to maintain proper chip thickness for the insert geometry. The lower lead angle also guides the cutting forces in the axial direction, up the spindle, which is more stable and easier on the machine. For this reason, when performing high feed operations, cutters should be operated at full diameter engagement, but no less than half their insert width. Cutters engaged at less than half their insert width will be subjected to a pushing effect. This will likely lead to increased vibration because the cut is unbalanced, the company said.
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